Principles of Lust
by Lunaschild2016
Summary: They had all thought that Eric and Four made waves when they hit that roof, it is nothing compared to these two. Especially when they catch the eyes of the two bitter enemies who have their own claims on them. Dauntless, batten down the hatches and get ready for the storm that is Kat and Eva. Eric/OC Four/OC M (Smut and launguage) AU NO WAR NO DIVERGENT HUNT
1. Chapter 1

**A/N: I had resolved not to start anymore stories until I updated my current ones more or finished them but that just isn't happening for me I guess. So all you lovely people can thank a few things for this story. Being snowed in and reminiscing with a friend about blasts from the past like Enigma and all their yummy sounds. This is where this story came from, after talking about and sharing links for music like Enigma, Motley Crue and 2Pac. I am looking at you sleepy1177. On your head this be too. :D Hope everyone is staying safe and warm...winter is certainly here.**

 _ **Disclaimer:"... a mind needs books as a sword needs a whetstone, if it is to keep its edge." ...(Game of Thrones) - My mind thrives and breathes in the world created by V Roth - She kindly lets me sharpen my wit upon the blade she has created.**_

 **Chapter 1**

He trailed a finger up the inside of her long and beautiful creamy skinned leg and chuckled deeply at her moan and shifting against the mattress. She was gorgeous laid there on his bed. Her curly dark blonde hair spread out behind her. Her long legs on her willowy frame rubbed together almost as if in anticipation for what was about to happen. She looked at him through those beautiful long lashes with her pouty lips parted and panting.

He hadn't been able to resist her even though he should have. They had both been too worked up from months of teasing and flirting. They were also both too drunk tonight to fight it like they normally did.

What got into him as he all but tossed her over his shoulder and took her to his apartment he couldn't even begin to say. But in this moment he didn't care either. Her naked and ready on his bed was all he saw as he positioned himself between her legs.

She looked down at him, her piercing grey eyes full of lust but also confusion. He knew then that even with all her bluster and talk she had never done this before. He would be the first.

He was pleased about this more than he could say. Oh how Eric was going to have a shit fit when he found out about this. He should stop. It wasn't right. It was just going to cause more drama and shit with Eric and him. He also knew he didn't give a fuck right now.

His mouth moved closer to her heat almost on its own. When his fingers parted her and her mouth opened slightly in a wonderful little shocked gasp he knew he wouldn't stop.

He gave her a slow and long lick, closing his eyes at the taste of her. Nothing could ever or would ever taste as sweet to him.

"Oh…" She moaned in surprise as her head fell back. She couldn't bring herself to lay all the way back. She propped up on her elbows so she could see him, watch him as he continued to bring her to pleasure.

His deep blue eyes held hers too while his tongue moved over her clit in circles. She could see the smirk in them and the smirk on his lips as he eased a finger inside of her.

Her breathing was becoming ragged but so was his. Fuck! He never knew this could be such a fucking turn on. Zeke had said it was but he had doubted how it could be. It was her eyes and her sounds. They were almost driving him crazy.

"Oh fuck...Four.." she panted as her hips started to move in time with his finger. Did he just fucking hum over her clit? Whatever he did it felt fucking amazing.

He was amazing with his long fingers and tongue. She was in so much trouble here. Would be in so much trouble if Eric ever found out. He would kill both of them. She couldn't stop either and didn't want to stop.

"Are you going to come for me Kat?" Four still kept his finger working in her and only paused his mouth working over her to ask that question. To tease her with words like she had been him for months.

"Yes...please don't stop." Kat moaned. Her forehead furrowed in frustration and pleasure all at the same time.

He didn't need to be told twice. So he dived back in but this time was a little more hurried in his attentions. He needed her release. Needed to see her come undone.

He didn't have to wait long. Her hands grasped his sheets and her mouth fell open as tremors started to rock her body. He felt her muscles gripping his finger and start to work over it. She was already so tight that it just became even tighter.

"Oh shit! Oh gods yes Four!" She cried out as the best orgasm she had ever had in her life racked her body.

Four lapped up her release then moved, kissing back up her body until he was positioned outside of her.

"Last chance to change your mind Katelyn." Four said in a voice hoarse with desire.

Kat could only shake her head back and forth as she wrapped her legs around his waist. She finally got her breath back. "I'm not changing it. I want you Four. Please…"

Four took a breath after he nodded and kissed her deeply. He couldn't deny he was and had been in deep with this girl from the first. He had just been fighting things because of Eva and Eric. Now they were barely thoughts in his mind. All he thought of was Katelyn and this. "Tobias. Call me Tobias please Katelyn."

Her heart did a flip at that. Knowing what that meant to him. "Tobias." She whispered with a smile.

Four's breath caught in his chest as he slowly started to push into her. She might have acted like she wasn't but he had known when they started she was a virgin. She had also known he was too but he had never made that a secret one way or the other.

They were losing it together as he slowly pushed in. Their eyes locked until he was all the way in. She had been biting her lip when he got to her barrier and he had claimed her mouth in a kiss, to swallow her pain if he could.

He stilled inside of her. Letting her adjust but also to let himself calm down. He didn't want it to end too soon and he was already so close. She moved her hips to let him know she was ok but he still continued to kiss her as he began to move again.

Kat moved her hips and inner muscles like she had researched on how to do. She might not have done the acts before but that didn't mean she shouldn't know how to please herself and the person she was with the first time. She and her best friend and secreted away books and vids to do what research they could.

None of that really prepared a girl for the real act. Now she knew those girls in those videos had to be faking or acting. Her sounds and faces could not have been as pretty or attractive as theirs.

She also didn't care because after the pain faded it felt amazing. She pulled him to her for a kiss. She loved his groans when she worked everything she had over him.

"Fuck Kat." Four pulled away to look down at her. He was getting so close and faster than he wanted.

Kat's eyes closed for a second as the waves started to build. "Oh god Tobias. I'm going to.." She was panting as she opened her eyes again.

She saw his own need for release in his eyes. "Come with baby." He murmured as his lips grazed against hers.

She couldn't help the small smile that crossed her face at him calling her baby. She nodded just before their mouths met again. Their thrusts and movements becoming more frantic as they tipped over the edge. She was first but not by much because as soon as her already tight walls closed around him there was no way he was holding out.

Their moans of release were captured by each other. They couldn't stop kissing or clutching to each other. When they finally came down, their bodies spent, Four gathered her to him and held her close.

Kat's head was already spinning from drinking as much as she had but now after that it was even more. She closed her eyes promising herself it would be just for a moment. She knew she needed to get dressed and leave before Eric figured shit out and went on a rampage looking for her. It felt so good in Four's arms though. Soon they were both passing out after he remembered the covers and pulled them over the two of them.


	2. Chapter 2

**Chapter 2**

He shouldn't be fucking doing this. That was the thought that was crossing his mind as he had her pressed up against the wall of his apartment. He couldn't stop himself and she wasn't helping matters either by her moans and little movements against him. Her legs were wrapped around his waist, their tops were off and he couldn't stop sucking and licking on her perfect fucking tits.

Fuck! He had spent nights just wondering what they would look and taste like. Her cry out when his teeth scraped against one nipple and he tugged on it gently had him smirking but it also made him pull back.

"Eva, we have to fucking stop." He groaned as he locked eyes with her. Those fucking azure eyes that always felt like they were digging into his soul and finding him lacking.

Eva frowned in frustration and shook her head with a scoff. "Giving up so soon Eric. What happened to a brave man never surrenders?" She mocked him knowing it would piss him off and challenge him.

"You and that fucking mouth, Stiff. I thought I told you that you needed to watch it."

He had let her slide to the floor but it just caused them both to groan as every bit of bare skin they had going on slid against each other. They were both in just their underwear at the moment. They had both dizzily stripped each other as soon as they got in his door. Barely fucking making it back to his place as it was with how attached they had been to each other.

He was sure that it drew looks and attention. Which was just fucking fantastic because that meant it would get back to Four that he was with his little stiff.

Eva got a wicked look just before she hurriedly flipped them so that she was pressing him to the wall and she was in front of him. "Want to see what else I can do with my mouth Eric?" She purred out at the same time she shoved his boxers down and then dropped to her knees.

It was the shots. That was the only logical reason she could come up with for her actions right now. The shots and the several beers she and her friend had just before they had made that fucking bet then went on their separate missions. She could tell herself it was all the shots but it wasn't. It was him and what he could do to her with just a look and those damn eyes.

He barely had time to register what she was doing before her hand was wrapped around his length. His nostrils flared even wider and it felt like he was punched in the gut with how fucking good her small hand felt wrapped around him. Her wavy honey hair was hanging free of it's normal ponytail or bun she wore it in.

That had started his undoing tonight. When she had sauntered up to him with shots in her fucking hands in her spaghetti strapped dress with that fucking plunging v neckline. Showing more skin than he thought she ever had in her life. He had wondered how the fuck she had gotten out of the door with Four like that. It was the hair though, cascading around her shoulders and glinting in the pulsing lights. The hair and the eyes. Fuck, who was he kidding it was everything. He had wanted to be buried inside of her from the moment she landed on the fucking roof.

Eva tried not to go dry in the mouth when she was eye level with his erection. She wasn't prepared for how solid, hot or big it was going to be. None of the books or videos had really prepared her for this in real life. She met his eyes though, he quirked an eyebrow in a challenge. He didn't think she would do it.

Remembering all her research and preparation she started by swirling her tongue over the head, tasting him and she moaned at the salty but addicting taste. She never lost her eye contact even when he let his head hit the wall for a moment and groaned but then immediately went back to holding her eyes.

It was the most erotic thing he had ever experienced. Never mind that her mouth was starting to wrap itself around him or her hand went to massage and cup his balls. It was her making sure to hold his eyes the entire time. What he saw in those eyes though. She had never done this before. She could fucking act all tough and like it was no big deal but he saw it there. The moment before he had challenged her she had been scared and intimidated.

He couldn't help the smirk that came over his face as he looked down at her. It was a brief one in thought of the fit Four was going to have over him defiling his precious little stiff. Because he was, he was going to wreck her and make her his.

His hands went to her head and helped guide her. "Fuck you look beautiful with your mouth wrapped around me baby." He groaned when she started to take more in her mouth as he guided her.

Eva was getting wet, wetter than she already had been. Her hand was moving up and down along his shaft as her mouth tried to take as much as possible in. She was getting unbelievably turned on by this and his moans. His chest heaving and nostrils flared. She had thought it was the sexiest thing she had seen when she had watched him fight. Now she knew that was wrong cause this was even hotter. Because she was doing this to him. Her the little stiff was making this man unravel for her.

She didn't realize her other hand had moved to start to touch herself until she heard his rumble that carried through his chest down to her. He pulled her away from her ministrations and then back to standing. Pulling her in for a searing kiss then he cupped her ass until she was once again wrapped around his waist.

He pulled away from the kiss as he walked them to his room. "You don't get to touch yourself Eva. Nothing touches you there but me. Either my mouth, fingers or my cock. Do you understand me?" He growled this just before he crashed his mouth to hers again.

It was clear he didn't expect an answer and he sure as hell wouldn't take anything else other than 'yes eric'. Which he knew she wouldn't give him. She was just too mouthy and full of fire to give in. It was what turned him on most about her.

He didn't even take the time to let her remove her underwear, he just ripped them off of her as he walked.

She pulled back from the kiss with a scowl. "Hey, those were my nice ones dammit."

Eric smirked as he kicked his bedroom door open more. "They were nice but I'll buy you better ones." Then he claimed her mouth in a kiss again.

As soon as he had her laid down though he was moving down her. He didn't waste anytime in making sure that his mouth and fingers were the first there. Her back arched as she gasped out but this only served to give him a better position. He moved so that her thighs were on his shoulders and she had a perfect view of what he was doing. It also allowed him to keep eye contact with her.

He slid a finger into her and groaned at how wet but tight she was. He had known that she was inexperienced to some level but that she was that inexperienced almost had him pulling back. Then their eyes met and she bit her lip. He knew there was no fucking way he was walking away from this.

Fuck Four. She was his now.

"Now you're going to find out what I can do with my mouth baby." He purred out just before he parted her then blew lightly on her center of nerves.

"Oh...oh shit." Eva cried, her back arching again. She wanted to scowl at his pleased smirk but then he started to lick in long slow motions. She could see his tongue dragging across her and her eyes almost rolled into the back of her head.

"Do you know how fucking amazing you taste?" Eric moaned as he closed his eyes for a moment and savored her. She did taste amazing and he knew he found his new favorite thing to do.

Especially with her soft little whimpers and moans that he got from her each time his fingers moved in her or he sucked on her clit. It didn't take long or much and he knew it wouldn't. She came hard and he lapped it up but kept going even after her trembling stopped.

"Oh gods...please Eric." Eva moaned. Her orgasm had been incredible and had happened before she even knew what was going on. But she wanted and needed more. So she could only beg the man. She knew he was eating that up by the wicked gleam in his eyes before he moved to start kissing up her body.

"Please what Stiff?" He purred near her mouth and rubbed himself along her folds.

"You know what Eric. Don't play games." She panted, trying to growl but it just wasn't happening. It only came out as an almost whimper and that would have normally pissed her off but she wasn't capable of that right now.

"Oh no. The time for games is over little stiff. And I was never playing, that was all you. So now I want you to tell me what you want and where you want it." He wasn't giving in until she gave him that.

She fought it too. She refused to say the words even though her body was screaming at her. It didn't help that as he slid his length along her he also started to work on her nipples again.

Gods he had a beautiful mouth. The things it was doing to her. No matter how she moved her hips she wasn't getting anywhere and his chuckle let her know he knew it too.

"Fuck it already Eric. Please. I want your cock inside of me now dammit." She yelled this even as her body flashed with red and Eric pulled back to look at her.

He couldn't help the pleased as shit smile he had but also just the lust from her lying there underneath him all flushed from desire and innocence. He was going to go to hell for this. He was sure there was some pre-war commandment about what he was about to do and with who he was about to do it to that would say he was going to hell. But fuck if it wouldn't be with a smile.

He leaned over her again and took her mouth in a kiss as he started to guide himself into her. When he got just the tip in he pulled back from the kiss just slightly. "It's going to hurt baby but I promise I will make it better."

That was all the warning he gave her before he pushed all the way through in one smooth and sure stroke. Not rough but not gentle either. Her nails dug into him but his mouth had claimed hers in a kiss just after he got the words out.

She was still gasping against him and not all from pain. His hand had moved to her clit and was gently rubbing circles the entire time. He stayed still when he was buried in her, kissing her deeply.

She was panting from the stimulation to her and it was driving any pain away and fast. Soon instinct and her body was guiding her and letting them both know she was ready for more as her hips started moving. She gasped for breath when he pulled away from the kiss, eased out and pushed back in. He was still keeping with the long smooth movements but he could only groan when felt her start to work her muscles over him.

"Fucking hell baby." He groaned.

This made Eva smirk slightly but she wasn't much better because he was still making those lovely little circles on her clit with his fingers. "Does that feel good Eric?" She gasped the question as her back arched when he pinched on her nerve bundle the tiniest amount.

"Too good Eva. Dammit...I am…" With a growl he started to pick up the pace as he started to push into her with more force.

He knew she was doing it on purpose to push his buttons as much as he was hers. She wanted him to lose it but he wanted the same from her too. Just like anything else with the two of them they were challenging each other.

"You are going to come first Eva." He growled and pulled out before he slammed back in her.

"Shit! Eric….not if I make you first." Eva panted and pulled his head down to her, sucking in his bottom lip and then biting down on it as she clenched her muscles around him.

Eric's chest rumbled with the groan he couldn't vocalize and felt his balls tightening. Dammit she was amazing. He didn't know how she knew what to do but however she knew it, it was driving him insane. It didn't help he hadn't been able to find any release with her on his mind all the damn time.

All he knew was now that he was getting this with her there would be no way it was just a one time deal. He let her have her fun with the kiss until he pulled away and moved to her neck. The free hand he had moved to wrap in her hair and tugged until her neck was bared for him.

He didn't even demand her to come because he knew this would do the trick. The same time he latched onto her pulse point he pinched her clit and slammed all the way into her hard.

A scream of pleasure tore from her throat and her muscles locked on him hard as her orgasm rocked her entire body. Hard enough to vibrate along his and pull his release from him too.

"Gods yes!" She cried out at the same time as his own shout of "Fuck Eva" tore from his chest. He pulled back and slammed into her one more time burying himself deep enough that he was sure she felt it at her womb. He couldn't help it. He wanted to make sure she was his and his body followed that directive.

Thank fuck they gave all the initiates shots that lasted six months.

Panting he dropped to lay beside her after they had both stopped shaking from their release. When he was laying down he jerked her to him and started to kiss, bite and suck along her shoulders and neck.

If she was thinking she would have stopped him. But her mind wasn't processing things at the moment because she was still really trying to come down from everything.

She moaned as he began to nibble on her ear. "What are you doing?" She sighed in a completely sated way.

Eric smirked against her ear and chuckled. "Just marking my territory."

This snapped her out of it and made her eyes snap open. She gasped and slapped a hand to her neck as if she could feel the damage he had just done. "Eric, please tell me you fucking didn't!"

He pulled back and looked at her, grabbing her chin and held her eyes. "Oh but I did. You're mine now Eva. You made that decision when you came up here with me. You know how I am. What did you expect?"

"For you to use that fucking brain and intelligence that I know you have beneath all that fucking scowling menace you put on. What did you think was going to happen when Four finds out this shit?" Eva could almost feel her panic starting to rise.

Eric wanted to snarl at his name coming from her but he didn't. "You should have thought of that before you chose me Eva. Don't worry about Four, I can handle him."

Eva slapped a hand to her head and closed her eyes with a groan. Her only prayer now to not be killed in a very painful way by Four was that Eric was too drunk to remember this. Lord knows she was still pretty messed up and she had made sure to keep feeding him shots. As if he was sensing her thoughts he chuckled.

"And if you are thinking I may not remember this, trust me there wouldn't be enough whiskey in the world to make me forget getting you in bed with me finally. Face it Eva you're mine. Fighting it will only make it worse for you." Eric pulled her back to him for a kiss while his hands went to tweak and tug on her nipples.

He had known early on that this particular stiff would like it a little rough and she had shown tonight that he was more than right. Her moans as he started to pinch her hardened and sensitive nipples let him know he was right. He smiled into her mouth even as her had went to move along his hardening member again.

Sleep wasn't coming for him anytime soon, but the two of them would be.


	3. Chapter 3

**A/N: Last chapter that I already had written out. Will be working on more later but am trying to be laser focused today and work on other stories among my other IRL duties and responsibilities. We will see where my mind takes me today though. Can't predict where that will be from hour to hour. Hope you are enjoying the fluff and fun!**

 **Chapter 3**

It wasn't until much later when two young women were able to finally pry themselves away from the two men that were locking them in their arms to try and keep them with them. In those separate apartments they dressed as quietly and quickly as possible. One of them decidedly missing a key pair of undergarments. Then they let themselves out of the apartments and walked gingerly but almost smugly towards their meeting place.

When they caught sight of each other they were each wearing smirks.

Eva and Kat came face to face and eyed each other and then looked around them.

"Not here. I also really need a shower ri

ght about now." Eva groaned softly.

Kat could only chuckle and nod. She wrapped her arm around her friend and the two walked, more than a little sore, along the path towards the dorm.

"Thank gods we get apartments or housing assignments soon. Well, when we find out our ranks anyways." Kat mused with a smirk.

Eva sighs and nods. "We were both neck and neck for first the entire time. You think we did good enough in our times to keep that up?"

Kat laughed and nodded. "We both had less ten fears and under five minutes. I am going to say it is going to be damn close."

"No hard feelings right? That is what we promised each other. That we wouldn't become them?" Eva looked to her friend worriedly.

Kat squeezed her side as they crossed over the Chasm to walk towards the dorms. "Of course! You should know that by now Eva. We aren't competing like they were and always are."

Eva chuckled and smirked over her. "Current bet not withstanding, right?"

Kat shrugged and smirked back at her. "Well the bet was more of the push we needed to get what we wanted. We can say it was us competing but…."

Eva sighed a little and then scowled. "The fucker marked me Kat. He just straight up told me to get over it and marked me."

Kat laughed and then held her hand over her mouth to try and hold in her laughter as they approached the dorms. "What did you expect Eva? It is Eric. You already knew what he was like from our experiences in training but then my stories as well."

"There is something wrong with us. You know that right? I mean who does what we did?" Eva chewed on her lip a little worriedly.

"Did what? What is wrong with what we did Eva? They are two single guys and we are two single girls." Kat replied with a shrug but in a whisper because the were right by the door to the dorm.

"Yeah but one is your older brother and the other is mine. Not to mention they are mortal enemies and we knew this. We still went after them."

"First of all we didn't do it because of those reasons and you know it. Like you said when you figured out how much you wanted my asshole brother, it's just chemical and not something we could control."

Eva breathes in through her nose and then nods firmly. "You're right, there is no reason I should feel guilty. I am a grown woman and can be with who I want to be."

Kat nodded proudly but they were both in the back of their minds worried about the fallout from the actions their drunken hormones caused them to take.

Eva and Kat were an odd pairing. A friendship born after failed attempts to visit their stubborn and asshole brother's when they had transferred to Dauntless.

They had both turned away their visitors, believing it was easier to make clean breaks because there was no way their little sisters would be going to Dauntless.

Amar had looked at the two with sympathy and inwardly was cursing the two most stubborn initiates he had ever had both the pleasure and displeasure to instruct. He had barely been able to handle their looks when their faces fell and looked crushed.

It had driven him to drag both of their asses to the training room and having them both do pushups, lunges, suicides and anything else he could think of until they were both heaving.

He had told the girls this laughingly over dinner recently.

As they had both walked out they had shared looks. Realizing both were distressed and with holes in their hearts from the loss of their big brothers. They had talked as they walked but had kept going until they ended up spending the entire day together.

How much they had in common while still being from almost different worlds. They, like their older brothers, were so very similar. The difference between the two girls and their brothers was that while in the boys it had driven them to become bitter rivals, for the girls it had driven them to become the closest of friends. Sisters almost. There was no secret they held from each other and while they loved to drive each other to do better and be better it did not turn into fierce competitions like with Eric and Four.

It hadn't taken them long to determine that they too were meant for Dauntless and they were going to join their brothers and best them come hell or high water. It also helped that Amar had taken it upon himself to help them out in the respect as well.

From the moment they landed on the roof their focus had been to do better than their brother's in everything they could. To show them how wrong they had been to cut them out of their lives and lose faith in them. They had done that spectacularly. They had also repaired their relationships with their brothers to a point. They still held hurt from their rejections. The girls had each other and it had driven them both to be the best and support each other.

Everything had been going well and to plan. A plan almost two years in the making from the time the first walked out of the compound with heavy hearts.

Everything but the two of them constantly fighting feelings and urges in regards to each other's sibling. They had admitted to each other first thing. Distressed that it would cause the two of them drama to to be torn apart. Oddly enough it did the opposite. Because in this two they shared the experience and frustration.

All through training they had separately dealt with taunting, teasing, almost kissing or moments of tension so great you could cut through it with a knife. It had been torture for them both because they were fighting so hard only because of the two men's hate for each other.

They fought until last night when they decided, rather drunkenly, that they shouldn't have to fight it. They were adults and they could explore. Who better to explore their first times with two men they respected and had such strong desires for. They were planning on it being a relief for their overly stimulated bodies.

A pure chemical reaction to someone that needed a chemical release to be able to stabilize. At least this is what Eva had concluded from her own observations of her interactions with Eric.

They didn't take long to shower, they never did because they hated sharing with some of the male initiates. It seemed like they were beacons for sleaze and pervs. They were thankful they had each other's backs and wicked moves….as a few of them had found out first hand.

"Coffee?" Kat asked as they stood in front of their beds, debating getting more sleep or just getting up and starting their day.

Eva chewed her lip and nodded. "I won't be able to get back to sleep. I should but I know I won't. Let's get coffee and something to eat."

With a nod the two girls linked arms again and walked out of the dorm. It was still early enough that they knew they wouldn't run into many people and hopefully Four and Eric were still blissfully asleep in their beds and would remain so for a time.


End file.
